It is known that the cornea of an eye can, in certain instances, be surgically reshaped to correct and improve vision. Where the condition being corrected is myopia or near-sightedness, the cornea is relatively flattened, whereas if hyperopia is being corrected, the cornea is relatively steepened.
In either case, as more fully set forth below, there are several different types of ophthalmic surgical procedures which can be employed for this purpose. Although the types of procedures may vary, the ultimate object in correcting myopia, for example, is the same. Namely, the object is to cause different types of tissues in the cornea. These include portions of the epithelium, Bowman's membrane, and the stroma.
The present invention recognizes that it is preferable to leave the epithelium and Bowman's membrane intact and to limit the tissue removal to only the stroma. Removal of tissue from the stroma results in the creation of a specially shaped cavity in the stroma layer of the cornea. When the cornea deforms in the intended manner, the desired flattening of the cornea results.
Further, the present invention recognizes that internal tissue "photodisruption," can be effectively accomplished using a pulsed laser energy if the irradiance of the beam, its focal spot size, and the proper layering of photodisruption sites are effectively controlled.
Accordingly, it is an object of the present invention to provide an improved method for performing intrastromal photodisruption on the cornea of an eye. Still another object of the present invention is to provide a method for intrastromal photodisruption which removes stromal tissue in a predetermined pattern to attain the desired flattening of the cornea. Yet another object of the present invention is to provide a method for intrastromal photodisruption which is relatively easy to perform and which is comparatively cost effective.